Jim Hendler wrote:
> (note - there is a suggestion to editors for some wording changes to Ref
> and Guide in this message - it is before the section marked personal
> opinion)
>
>
> At 8:44 AM +0300 5/14/03, Jeremy Carroll wrote:
>
>> In
>> http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0181.html
>>
>> DanC:
>>
>>> On closer examination of the comment, it seems
>>> to be more about what goes in OWL DL than
>>> what goes in OWL Lite.
>>
>>
>> And in ...
>> http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0174.html
>> DanC:
>>
>>> Please help me find the relevant decisions
>>> and/or find evidence that those implementations
>>> pass some relevant tests and/or add an
>>> issue to the issues list.
>>
>>
>> In January, we agreed a definition of a "complete OWL DL consistency
>> checker",
>> if we had evidence that such a thing existed, and/or that more than
>> one would
>> exist in the future (and the WG was satisfied that they would be
>> practically
>> usable, rather than essentially theoretical exercises) then we could
>> respond
>> with a message that indicated that, and that we thought that that was
>> sufficient to justify the DL level.
>>
>> If we don't have such evidence then I agree with
>> http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0181.html
>>
>> DanC:
>>
>>> Mr. Merry's point, "We're concerned that OWL users should have their
>>> expectations met when they use OWL compliant systems." seems well
>>> made, no?
>
>
>
> So let's set their expectations correctly -- we did try, by the way - in
> Reference, section 8.2 we say:
>
> In particular, the OWL DL restrictions allow the maximal subset of OWL
> Full against which current research can assure that a decidable
> reasoning procedure can exist for an OWL reasoner.
>
> and in 8.3 we say
>
> The limitations on OWL Lite place it in a lower complexity class than
> OWL DL. This can have a positive impact on the efficiency of complete
> reasoners for OWL Lite.
>
>
> In fact, my original response to Mr. Merry was going to be that we had
> already addressed his comments and point out these quotes --- However,
> his comments and a couple of others we received show that we haven't
> made the difference clear ENOUGH in our documents. (For example, in
> section 1.2 we don't mention the computational issue). I therefore
> suggest that editing Ref and Guide to set expectations is the correct
> solution - consistent w/WG decisions in the past.
>
>
> One we could fix ref, is to make it clear that the difference between
> OWL Lite and OWL DL with respect to this computational issue is there.
> For example, when we first introduce Lite in section 1.2 of ref we say:
>
> OWL Lite is particularly targeted at tool builders, who want to support
> OWL, but want to start with a relatively simple basic set of language
> features.
>
> instead of saying it is known to have a relatively efficient decision
> procedure (and citing the literature). Maybe simply adding a sentence
> after the one I cite above that says
>
> "In addition, OWL Lite is designed based to fit into a known
> computational class that, while exponential, is lower than the
> complexity of OWL DL [cite something]"
>
I agree with this change.
Also, I think the sentence earlier in this section (1.2) on OWL DL needs
to be changed (as Dan also pointed out). It currently says:
[[
The main reason for having the OWL DL sublanguage is that tool builders
have developed powerful reasoning systems which support ontologies
constrained by the restrictions required for OWL DL.
]]
This requires some form of not pointing to the issues discussed by Ian
in his December message on complexity:
http://lists.w3.org/Archives/Public/www-webont-wg/2002Dec/0239.html
I wouldn't mind incorporating Ian's message in some (edited) form into
Ref, e.g. as extended note, as a new Sec. 8.4 (probably my preference)
or as appendix.
Guus
> I also think the "Species of OWL" section of the Guide is also less
> clear than it could be, and might be wordsmithed to make the issue
> clearer (for example, OWL Lite could say "Desirable computational
> properties" and OWL DL could say "maximal decidable subset, although
> subject to a higher worst-case complexity")
>
> Guus, Mike S -- would making these edits be acceptable? If so, I would
> include in the response to Merry and to the other similar issues.
>
>
>
> <PERSONAL OPINION>
>
>
>> (A danger is that if OWL DL is tainted then the whole OWL brand is
>> tainted).
>>
>>> Jeremy
>
>
> What I would say would make OWL DL "tainted" would be to remove oneOf
> and hasValue. hasValue is used in about 10% of the ontologies in the
> DAML ontology library, and oneOf, although not heavily used in that
> library, is IMHO necessary for mapping existing sources into ontologies
> --my group has used it in many cases where we have used either an XML
> schema or a database schema as the basis of an ontology, especially in
> our work with Web Service Composition [1]. I would also remind the
> group that we actually had support in the WG to put hasValue in Lite,
> but decided not to due to the computational issue.
>
> I would argue strongly that it is better to explain things more clearly
> in our documents than to change the language. We spent a long time
> developing a language that is well balanced for many considerations, and
> I'd like to see if used in practice before we start cutting useful
> features because of computational issues that may rarely or never arise
> in real applications. For instance, PARKA-DB [2], still the fastest
> ontology management system deployed to date, is in the same complexity
> class as OWL DL, but somehow people don't seem to mind since it can
> answer most useful queries in a few milliseconds against ontologies with
> tens of thousands of classes - it has a worst case time that could be in
> several minutes for the largest ontologies built yet - but that doesn't
> seem to matter since after 5 seconds it asks the user if they want to
> continue, and most people say "no" and reformulate the query...
>
> Quoting one of our comment raisers, speaking about OWL:
>
> At 11:43 PM -0400 5/9/03, Bijan Parsia wrote in [3]:
> 4) Get the damn thing out the door.
>
> </PERSONAL OPINION>
>
>
> [1] http://www.mindswap.org/papers/composition.pdf
> [2] http://www.cs.umd.edu/projects/plus/Parka/aaai97.ps
> [3]
> http://lists.w3.org/Archives/Public/public-webont-comments/2003May/0069.html
>
>
--
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